Problem: William ate 1 slice of pie. Umaima ate 3 slices. If there were initially 9 slices, what fraction of the pie is remaining?
$\text{fraction of pie eaten} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 4 slices, which leaves 5 out of 9 slices remaining. There is $\dfrac{5}{9}$ of the pie remaining.